Screw feeder for feeding sewage sludge or the like to a combustion chamber



Sept. 3, 1968 w. A. Hmscunew 3,399,637

SCREW FEEDER FOR FEEDING SEWAGE SLUDGE OR THE LIKE TO A COMBUSTION CHAMBER Filed May l0. 1967 10 Sheets-Sheet 1 INVENTOR. WILL/M l. HIRSCHFIELD ATTORNEY Sept. 3, 1968 w. A. HIRSCHFIELD 3,399,637

SCREW FEEDER FOR FEEDING SEWAGE SLUDGE OR THE LIKE TO A COMBUSTION CHAMBER l0 Sheets-Sheet 2 Filed May 10, 1967 w 7 l Rb fiw. mm w mm r F I I l I II If I I I I I ll llll w M MA7\ W n m m M/ n I: M B PL \N w F mm Sept. 3, 1968 w. A. HIRSCHFIELD 3,399,637

SCREW FEEDER FOR FEEDING SEWAGE SLUDGE OR THE LIKE TO A COMBUSTION CHAMBER Filed May 10, 1967 10 Sheets-Sheet 3 INVENTOR. WILL MM 4. H/RSCHF/EL D a rroen/s r Sept. 3, 1968 w. A. HIRSCHFIELD 3,399,637 SCREW FEEDER FOR FEEDING SEWAGE SLUDGE OR THE LIKE TO A COMBUSTION CHAMBER l0 Sheets-Sheet 4 Filed May 10, 1967 5 INVENTOR. I [5 I WILLIAM A. H/RSCHF/ELD ATTORNEY p 1968 w. A. HIRSCHFIELD 3,399,637

SCREW FEEDER FOR FEEDING SEWAGE SLUDGE OR THE LIKE TO A COMBUSTION CHAMBER Filed May 10, 1967 10 Sheets-Sheet 5 INVENTOR. W/L 1. MM 4. H/RSCHF/ELO A r ran/v5) INVENTOR.

1O Sheets-Sheet 6 w. A. HIRSCHFIELD SCREW FEEDER FOR FEEDING SEWAGE SLUDGE OR THE LIKE TO A COMBUSTION CHAMBER Sept. 3, 1968 Filed May 10, 1967 m. E v: E M H M A 4 M m/Ww L Y L MB Sept, 3, 1968 w. A. HIRSCHFIELD 3,399,637

SCREW FEEDER FOR FEEDING SEWAGE SLUDGE OR THE LIKE TO A COMBUSTION CHAMBER l0 Sheets-Sheet 7 Filed May 10, 1967 INVENTOR. WILL/AM A. H/RSCHF/ELD fm %%x4% ATTORNEY Sept. 3, 1968 w. A. HIRSCHFIELD 3,

SCREW FEEDER FOR FEEDING SEWAGE SLUDGE OR THE LIKE TO A COMBUSTION CHAMBER l0 Sheets-Sheet 8 Filed May 10, 1967 INVENTOR. W/L LIAM A. H/RSCHF/ELD A TTORNE') Sept. 3, 1968 w. A. HIRSCHFIELD 3,399,637

SCREW FEEDER FOR FEEDING, SEWAGE SLUDGE OR THE LIKE TO A COMBUSTION CHAMBER 1O Sheets-Sheet 9 Filed May 10, 1967 INVENTOR. WILL MM 4. H/RSCHF/ELD ATTORNEY Sept. 3, 1968 w. A. HIRSCHFIELD 3,399,637

SCREW FEEDER FOR FEEDING SEWAGE SLUDGE OR THE LIKE TO A COIVBUSTIQN CHAMBER Filed May 10, 1967 10 Sheets-Sheet l0 INVENTOR. WILL MM A. H/RSCHF/ELD WMN Z ATTORNEY United States Patent C SCREW FEEDER FOR FEEDING SEWAGE SLUDGE OR THE LIKE TO A COMBUSTION CHAMBER William Arthur Hirschfield, Fairfield, Conn., assignor to Dorr-Oliver Incorporated, Stamford, Conn., a corporation of Delaware Filed May 10, 1967, Ser. No. 637,394 Claims. (Cl. 1108) ABSTRACT OF THE DISCLOSURE This invention provides improved apparatus for feeding of high-moisture organic waste material or dewatered sewage sludge from a source of supply such as a hopper or conveyor into a combustion unit, through a screw feeder into which the waste material is packed by means of rotary paddles insuring continuity of progress of the Waste material through the feeder.

This invention involves the combustion of high-moisture organic waste, such as mechanically dewatered sewage sludge or the like, in a combustion unit preferably of the type containing a bed of granular heat-storing and heat-radiating material, such as sand, maintained in a hot fluidized state.

Mechanically dewatered sewage sludge as herein understood may be the result of continuous vacuum filtration or of centrifugation of clarifier underflow or the like. The high-moisture cake material thus derived may be in the form of a more or less stiff or substantially plastic or pasty mass which may possess considerable coherence due to the cellulosic or fibrous matter contained therein.

Such as mass, having a total solids concentration that may range from about to about 50%, is difficult to feed because of bridging or tunnelling or backing up of the material when delivered for example to a feeder screw at the higher concentrations.

The combustion unit may be of the kind wherein hot fiuidizing gases and/or combustion air are forced upwardly from a wind chamber through a constriction plate into a combustion chamber proper the lower portion of which contains the bed of the hot fluidized sand. The dewatered sludge or cake material as above defined may be subjected to rapid combustion substantially within the body or bed of hot fluidized sand. More particularly, and by way of example, this may be a combustion unit substantially as disclosed in the copending patent application of Albertson and Kilmer, Ser. No. 356,211 filed Mar. 31, 1964, employing an extrusion screw for feeding the mechanically dewatered cake material or sewage sludge of the higher solids concentration and compacted into the form of a plug, through the wall of the combustion chamber directly into the lower portion of the bed of hot fluidized sand.

The invention provides improved feeding apparatus effective to prevent tunnelling of the material in the screw feeder device, where dewatered raw sewage sludges of the higher consistencies are involved.

The term tunnelling here denotes a state or phenomenon which may occur where the feed material descending for instance from a feed hopper or conveyor, bridges or forms a tunnel conforming to the peripheral contour of the screw, thus interrupting the progress of the material which must be forced through the discharge end of the screw housing.

For the purposes of this invention, the screw feeder device is structurally and cooperatively combined with an auxiliary paddle device preferably integrated in the structure of the screw feeder apparatus, the object being to insure continuity in the progress of the feed material.

3,399,637 Patented Sept. 3, 1968 To this end, the supply duct or neck of the feeder housing is formed with a pair or semi-cylindrical symmetrical bulges or internal concavities opposite to one another and spaced upwardly from the feeder screw. Each of these concavities has concentrically mounted therein a paddle shaft having radially extending paddles or plates, which shafts are driven synchronously and counterrotationally in such a manner that only when the paddles move downwardly will they engage the descending feed material between them symmetrically from both sides so as to pack the material into the screw, while during the balance of their rotation moving upwardly within the respective concavities they are shielded from the feed material.

In this way, bridging is avoided both above and below the zone wherein the paddles operate, the paddles providing suflicient supplemental force to overcome the discharge resistance. The action of the paddles is first to engage material from both sides forcing it away from the walls while also exerting a downward pull upon the material, and then packing it into the feeder screw.

One feature of this embodiment lies in so locating the paddle shafts that only an intermediate portion of the downward packing or anti-bridging movement of the paddles is utilized.

The dewatered sewage sludge, for instance a mixture of dewatered primary and secondary sewage sludge, may be of a relatively lower solids concentration, or higher water content. For such a condition the invention provides a positive progressive displacement pump or so-called Moyno pump for feeding the sludge into the combustion chamber, combined with a screw feeder and a paddle device. The packing effect of the paddle device operating at the inlet end of the screw feeder prevents the Moyno pump at the discharge end of the screw feeder from causing air to be drawn or channelled through the inlet end of the screw feeder housing.

Because of the lower viscosity of such a sludge the feed device, that is the screw feeder with paddle device and Moyno pump, may be located remote from the combustion unit, connected thereto by a pipe or hose.

According to the invention, two or more screw feeders may be arranged parallel side-by-side to one another in a single feeder housing, each being coupled to a respective Moyno pump, but served by a single paddle device with a pair of paddle shafts extending transversely of the axis of the feeder screws. The pumps each through a pipe or hose connection may feed sludge to respective points of one combustion unit, or to separate combustion units. The packing effect of this paddle device in the single as well as the multiple feeder arrangement provides sufficient pressure at the inlet end of the pump or pumps to provide line pressures at the discharge end enabling the sludge to be moved or pumped through pipe or hose of a substantial length.

In a preferred embodiment of a multiple screw feeder of this invention, the unit comprises two pairs of screw feeders so arranged that one pair may be operated separate from, or without the other pair, thus allowing one or the other pair to be shut down, or to be overhauled. The invention also provides for the supply of feed sludge to be delivered selectively to the one or to the other pair of screw feeders.

Other features and advantages will hereinafter appear.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within the metes and bounds of the claims, or of forms that are their functional as well as conjointly cooperative equivalents, are therefore intended to be embraced by those claims.

FIG. 1 is a diagrammatic showing of an example of a waste disposal system including a waste combustion unit equipped with the feed apparatus according to one form of this invention.

FIG. 2 is an enlarged view taken from FIG. 1, more clearly showing the feed devices and other accessories relative to the combustion unit.

FIG. 3 is a greatly enlarged fragmentary side view of the feed apparatus taken from FIG. 2.

FIG. 4 is a top view of the feed apparatus taken on line 4.4 in FIG. 3.

.FIG. 5 is an endview taken on line 55 in FIG. 3, showing the drive end of the feeding apparatus.

FIG. 6 is a cross-section of the feeding apparatus taken on line 66 of FIG. 3, showing the relationship of the feeder paddles to the feeder screw.

FIGS. 7, 8, 9, 10 are semi-diagrammatic views illustrating the operation of the feeding apparatus.

FIG. 11 shows another embodiment of the invention, comprising a remotely located feeding apparatus piped to the combustion unit for sludge delivery thereto from a multiple screw feeder unit.

FIG. 11a shows a modification in the arrangement of FIG. 11.

FIG. 12 shows a diagrammatic cross-sectional View taken on line 1212 in FIG. 11, of the combustion unit, with a pipe system connecting it to the multiple feeder unit.

FIG. 13 is a greatly enlarged side view of the multiple feeder unit.

FIG. 14 is a horizontal part-sectional view of the multiple feeder unit, taken on line 14-14 in FIG. 13.

FIG. 15 is another part-sectional view of the multiple feeder unit taken on line 15-15 in FIG. 13.

In the example illustrated in FIGS. 1 and 2, the invention is embodied in an apparatus for extrusion-feeding a mechanically dewatered sewage sludge into a combustion unit 10. This waste material may be derived (see FIG. 1) from a clarification and concentration operation which comprise feeding raw sewage 11 to a clarifier 12 delivering underfiow or dilute sludge to a sedimentation thickener 13 for further concentration. A sludge pump 14 which may be a diaphragm pump or a continuous progressive cavity pump also known as a Moyno pump, supplies the thickened sludge which may have about 5% to 10% solids concentration to a dewatering apparatus producing what is herein termed a mechanically dewatered sewage sludge. Such apparatus may be in the form of a centrifugal machine, or as herein shown in the form of a continuous rotary vacuum drum filter 15 delivering a filter cake which may have a moisture content in a range from about 25% to about 50% This waste material is then extruded in the form of a strand or plug into the combustion unit 10 by way of the feeding apparatus embodying the invention, and which in the present example is represented by the apparatus assembly A to be described below.

A blower 16 supplies combustion air to a wind box 17 of the combustion unit, forcing the air upwardly through an orifice plate or constriction plate 18 into the combustion chamber 19 which contains in inventory or body of inert granular material 20 having heat-storing and heatradiating capability, such as sand. This granular material is maintained in a state of teeter or fluidization. A free board space 21 is provided above the body or bed of fluidized sand. 7

The combustion unit also has a fuel burner 21a which may use gaseous or liquid fuel, with fuel supply indicated at 21b, primary air at 21c, and secondary air at 21d, all being supplied under sufficient pressure to enable the combustion gases to fluidize the sand while establishing the necessary bed temperature for the combustion of the waste material or mechanically dewatered sewage sludge. If the combustible organic solids content of the material be sufliciently high, say in the order of about 50%, the combustion may be self-sustainable with the burner shut off and combustion air supplied from the blower 16. For material of higher 'moistur'e'conte'nt, supplemental heat may be supplied by the" burner. An airp'reheater or heat exchanger- (notshow'n) may be provided for the combustion'air, which recovers and utilizes a portion: of the 'heat of the combustion gases from the stack. This air preheater may be used alone or in conjunction with the supplemental fuel combustion, depending upon the heat requirements or moisture content of the mechanically dewatered sludge. A scrubber S intercepts the fly ash or dust particles in the combustion gases.

In this example, the waste or cake material from the vacuum drum filter falls onto a horizontal belt conveyor 22 which delivers it through a downwardly directed neck 23 to the aforementioned feed apparatus assembly A whereby the material is compacted and finally extruded in the form of a plug into the combustion chamber or fluidized bed. r

In the present example, the apparatus assembly A comprises an extrusion feeder screw 24 having a shaft 24a rotating in an extruder housing 25 which has a straight body portion 25a, a tapered intermediate portion 25b, and a cylindrical delivery mouth portion 250 extending through the wall of the combustion chamber. The extrusion screw is correspondingly shaped with a tapering end portion but terminates a substantial distance k short of the end of the mouth portion, so that a plug of the material always remains therein as a seal.

An upwardly extending feed neck 26 of the screw feeder housing contains a paddle device 28 cooperating with the feeder screw in a manner furthermore to be described below. Above this paddle device the feeder housing joins the downwardly directed delivery neck of the band conveyor at a junction which comprises a pair of inclined mating flanges 27a and 27b.

. The apparatus assembly also comprises a variable speed motor 28a mounted upon a movable support structure, for driving the feeder screw as Well as the paddle device through transmission means 29 more clearly shown in FIG. 5.

In this embodiment, the apparatus assembly is mounted on a support structure 30 which in turn is movable on tracks 30a towards and away from the combustion unit in order that the delivery mouth portion of the housing may be retracted. For that purpose also there is provided a stuffing box or thelike which seals this mouth portion relative to the wall of the combustion chamber.

Retracting the apparatus assembly A on tracks 30a is for the purpose of withdrawing the projecting end of the mouth portion 250 sufficiently far into the protection of the thick retracting wall of the combustion chamber to avoid overheating of the mouth portion and of the plug of residual material therein during periods when the supply of feed material is stopped as during temporary shutdown of the combustion unit. In such instance, the supply of material from the conveyor band is stopped while the screw feeder continues until substantially cleared of residual material except for the residual sealing plug in the mouth portion 25c. The apparatus assembly is then retracted, separating the inclined flanges 27a and 2712 from another.

The paddle device comprises a pair of semi-cylindrical outward bulges or internal concavities 31 and 32 formed in respective side walls of the upwardly extending neck, arranged to extend parallel to the' axis of the feeder screw. These concavities are spaced upwardly as well as laterally from the screw axis substantially symmetrical relative to each other and to the screw, such spacing being tentatively indicated'by the horizontal distances 2: and the vertical distance b. A pair of paddle shafts 33 and 34 each'having radially extending paddle blades or plates and 36 extending in opposite directions from the shaft, are mounted for rotation in the respective concavities concentric therewith and parallel to the screw axis. The paddle blades of the two shafts when horizontally aligned as indicated in FIG. 6 (in dot-and-dash lines) have their inner tips spaced apart a relatively small distance a'1.

The concavities 31 and 32 themselves are so constructed and arranged that only when paddle plates move substantially downwardly counter-rotationally and symmetrically, will they engage the descending feed material between them from both sides tamping or compacting it down into the feeder screw, whereas during the balance of their rotation moving substantially upwardly within the respective concavities they are shielded from the descending feed material.

The drive transmitting means 29 (see FIGS. 4 and 5) comprise endless drive element or V-belt 37 through which the motor drives a large sprocket 38 fixed upon the shaft of the feeder screw. A much smaller sprocket 39 also fixed upon this shaft has driving engagement with a chain 40 which in turn engages a pair of large sprockets 41 and 42 fixed upon the respective paddle shafts, driving them counter-rotationally as indicated by arrows A-1 and A-2.

The timing of the drive means through chain 40 is such that the paddle plates on the respective paddle shafts will move counter-rotationally and symmetrically, and in a manner to prevent bridging or tunnelling of the material by the feeder screw, as illustrated more particularly and semi-diagrammatically in FIGS. 7, 8, 9, 10.

A vertical frame 43 supports bearing means 44a and 44b for the driven ends of the paddle shafts, as well as an adjustable idler sprocket 45 for the chain.

In the operation of the system, the dewatered sewage sludge may be supplied, for instance by the vacuum filter or a solid bowl type centrifuge at a substantially constant rate at which the conveyor belt and the feed apparatus assembly A in turn supply it to the combustion unit. If under these conditions the inlet end of the feeder screw is only partially filled then the paddle may run substantially idle due to substantially free fall of the material from the conveyor to the screw. However, with the material building up in the neck, the screw instead of feeding continuously would cause bridging or tunnelling of the material along the periphery of the screw as indicated at 46 in FIG. 7. This phenomenon or bottleneck is avoided by the operation and timing of the two paddle shafts cooperating with each other and with the feeder screw in the manner indicated in FIGS. 7, 8, 9, l0.

' In the vertical position (see FIG. 1) the paddle plates are fully shielded in the respective lateral bulges of the neck. In FIG. 8 the then upper pair of plates moving from their shielded position towards each other come to grips symmetrically with the descending material, displacing it downwardly into the screw, while the opposite pair of paddle plates remain shielded in the bulges especially with the paddle shafts recessed a horizontal distance d2 into respective concavities. The paddles when moving out of the upper portion of the concavities towards each other pull the material away from the walls of the duct and then downwardly towards the feeder screw.

In FIG. 9 the paddle plates have reached their horizontal position along with a corresponding further downward displacement of the material into the screw. In the subequent final phase of their effective movement indicated in FIG. 10, the material is tamped down fully by the plates and compacted into the feeder screw which extrudes the material into the combustion chamber, whereupon the opposite set of paddle plates becomes effective. Any small amount of excess material 47 (see FIG. 10) that might become trapped in the bulges is thus automatically returned to the material descending into the neck.

The embodiment of FIG. 11 exemplifies the use of a multiple screw feeder unit of this invention, located remote from the combustion unit.

A combustion unit 48, while similar to the one of FIGS. 1 and 2 described above, is provided with a multiple arrangement of sludge feed guns 49. In this example, two pairs of such feed guns deliver the sludge into the bed 50 of hot fluidized sand, at points equally spaced from one another along the periphery of the bed combustion chamber, although one pair of such feed guns is visible in FIG. 11.

In a multiple feeder unit 57 in FIG. 12 the pumps have delivery ends 58 connected to the respective feed guns via respective conduits 5?.

The bed of sand is supported upon a constriction plate 51 which divides the combustion space 52 above from the wind chamber 53 below. A fuel burner is indicated at 54, air supply at 55. Combustion gases from the combustion of the dewatered sewage sludge fed to the combustion chamber along with the resulting ash escaping through stack 56.

The enlarged cross-section of the combustion unit in FIG. 12, shown along with a plan view of the multiple feeder unit, indicates the location of the two pairs of sludge feed guns on the combustion unit, supplied from the multiple feeder unit 57. The feeder unit in turn may be supplied, for example, by a pair of continuous rotary drum filters 60 and 61 delivering to respective pairs of feeder screws which (see FIG. 1) pairs of screws P-1 and P-2 are separated by a vertical partition wall extending upwardly to the receiving hopper.

The upper end 62 of the partition is hinged at 63, so it can be swung (see FIG. 11a) to the right, allowing the filter 61 to deliver to the pair P-l, or be swung to the left, allowing filter 60 to deliver to pair P-Z of feeder screws. When the swingable part is in the vertical position, each drum filter supplies the associated pair of feeder screws.

In an alternative arrangement (see FIG. 11a) a single drum filter delivers to both pairs of feeder screws P-3 and P-4 respectively, separated by the vertical partition 64 which has a swingable upper end portion or plate member 65 allowing the filter to deliver either to the pair P-3 or to the pair P-4 depending upon the angular position of the plate member 65, as indicated in dot-anddash. With the swingable plate member in vertical position, both pairs of feeder screws will be equally supplied.

Whereas, for simplicitys sake, the filters in FIGS. 11 and 11a are shown delivering directly into the feeder unit, in practical construction a horizontal conveyor belt would preferably be interposed between the filters and the feeder unit.

Both in FIGS. 11:: and 12, a single paddle device 66 is indicated with a pair of paddle shafts 66a and 66b extending transversely of the axis of the two pairs of feeder screws, and rotated by a drive unit 67.

In the example of a multiple screw feeder unit 57 as shown in the greatly enlarged FIGS. 13, l4, 15, four feeder screws 68 are mounted parallel to one another and side by side, in a common housing structure 69.

The housing structure comprises a body portion or box 70 having a bottom 70a, side walls 70b and 700, a rear wall 70d and a front wall 702. The front wall has four tubular extensions 71 accommodating the forward end portion E1 of the respective feeder screws, the major rearward end portion E-2 of the screws being exposed to the descending feed material or dewatered sewage sludge in the box. The rear wall of the box has rearward extensions 72 providing bearing support for the respective feeder screw shafts.

Each of the forward tubular extensions is flange-connected to a well known Moyno pump M, that is a positive progressive displacement pump. In this pump an elongated rotary member 73 which looks somewhat like a twisted shaft, is coaxially coupled with the associated feeder screw, and cooperates with the correspondingly shaped inner hard rubber or the like surface 74 of a surrounding housing member 75, to produce suction at the inlet end, and positive progressive displacement of the material through the pump. A pair :of flanges 76 and 77 in turn connect the discharge end of each Moyno pump with a respective conduit or pipe or hose 78 leading to a respective feeder gun 49 on the combustion unit. These are the conduits shown in FIG. 12 in singlelines.

The multiple feeder unit in FIGS. l3, 14, is mounted on a base plate 79 by means of a pair of bearing supports 80 and 81 for each pump section of the assembly, a similar bearing support 82 for each of the rearward extensions, and support members 83 and 84 for the box.

The box has a horizontal top flange 85 to which is flange-connected a paddle device 86 shown to be of a height H-l. In this device a pair of paddle shafts 88 and 89 are mounted in a housing 87 which comprises an intermediate enlarged portion 87a of height H-2, a downward neck portion 87d of height H-3, and an upward neck portion 870 of height H-4. This housing, in other words, is in the form of a vertical duct of height H-l of a rectangular cross-sectional area matching the open area of the box, and formed with symmetrically disposed semi-cylindrical bulges or concavities B1 and B-2 extending rearwardly and forwardly respectively from this vertical duct. An access door 88 is provided at one side of this housing.

The semi-cylindrical bulges accommodate the paddle plate substantially as in the above described embodiment of FIGS. 1 to 10. The paddle shafts extending transversely of the axes of the feeder screws, are rotated counter-rotationally and in synchronism by means of drive motor 91 supported on the housing of the paddle device, and drive chain 92. By reason of being shielded during this upward movement in the semi-cylindrical bulges B-1 and B-2 during their upward movement, the paddles or paddle plates 90 on the shafts will engage the descending feed sludge only during their downward movement, thus packing it down into the exposed portions of the feeder screws in the box. This together with the fact that the forward end portions of the feeder screws are shielded in the respective forward tubular extensions 71, insures continuous progress of the waste material through the feeder unit and then through the pipe conduit into the combustion chamber.

The downward packing pressure exerted by the paddle plates at the inlet end of the pumps insures not only equal load distribution of the feed material to the exposed portions of the feeder screws within the box and optimum displacement efiiciency of the pumps, but also provides sufficient supplemental line pressures at the .pump discharge end enabling the sludge to be moved through a pipe or hose over a substantial distance. For example, a transmission length from the feeder unit to the combustion unit of about 50 to 100 feet more or less depending upon the consistency of the material and the characteristics of the pump can thus be made practically feasible in this operation.

This multiple feeder screw construction with paddle device is operable with all feeder screws in operation and equally supplied and equally driven, or else in the selective manner indicated in FIG. 11 or 11a and described above. Accordingly, in FIGS. 14 and 15 a vertical pa-rtition wall 93 is shown to divide the box of the housing structure so that one pair of feeder screws is functionally separated from the other, each pair having its own drive unit M-1 and M-2 respectively (see FIG. 12). A similar partition wall divides the paddle device with the paddle shafts extending through this partition and paddle blades or plates operating at either side thereof. An upward terminal portion of the partitioning structure may be movable as indicated in FIG. 11 described above, for selectively confining the supply of feed sludge either to one or the other pair of feeder screws. However, it should be understood that there are various other ways of selectively confining the feed supply to a respective pair of feeder screws. Also each group of feeder screws may comprise more or less than the pair illustrated in the example of the multiple screw feeder unit. Also, the point of introduction of the waste material into the combustion unit may be in a zone other than the one herein shown, including the free board zone above the fluidized bed. Furthermore, the feeder apparatus of this invention is applicable to combustion units other than the type herein illustrated.

From the foregoing it will be seen that the invention enables a combustion unit to handle a high-moisture organic waste material in the nature of a mechanically dewatered sewage sludge so that material will be extruded into the combustion chamber uniformly and without interruption, by the cooperation of the paddle device with the feeder screw or screws, arranged and timed with respect to one another substantially as herein shown.

Each of the sludge feed guns 49 (see FIG. 12) may have an air cooling jacket (not shown) provided with an air supply from supply pipe 78a. connected to distributing pipes 7 812, 78c, and 78d.

However, it should also be understood that each of the elements of the system or apparatus, or two or more together, may also find a useful application in other types of extrusion feeding systems differing from the type described above.

While the invention has been illustrated and described as embodied in a system for sewage sludge disposal by combustion, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing from the spirit of the present invention.

Iclaim:

1. In a sewage treatment and disposal system for producing organic waste material for disposal by combustion, the combination which comprises a combustion unit having a combustion chamber, a horizontal feeder screw, a housing wherein said screw is mounted for rotation, said housing having a delivery end portion connected to said combustion chamber in sealed relationship therewith and having an upwardly directed vertical supply neck through which the waste material passes downwardly from a source of supply to said screw, a paddle device which comprises a pair of semi-cylindrical internal concavities formed symmetrically in opposite walls of said neck, a horizontal paddle shaft with radially extending paddles mounted for rotation in each of said concavities concentric therewith, said concavities being so constructed and arranged that only when the paddles move substantially downwardly counter-rotationally will they engage the descending feed material between them from both sides so as to pack the material into the screw, whereas during the balance of their rotation moving substantially upwardly within the respective concavities they are shielded from the descending feed material, means for counter-rotationally rotating said paddle shafts while rotating said feeder screw, and means for supplying said waste material to said upwardly directed neck and to said paddle device.

2. The combination according to claim 1, wherein a conveyor delivers the material to said paddle device.

3. The combination according to claim 1, wherein said opposite walls are substantially vertically parallel to one another, and wherein said concavities therein are so shaped and dimensioned that the paddle shafts concentrac therewith are spaced a distance horizontally outwardly from the respective planes of said walls, thereby limiting the initial eifect of the paddles upon the descending material.

4. The combination according to claim 1, wherein said drive means comprise a drive for said feeder screw, a small sprocket on said feeder screw, a relatively large identical sprocket on each paddle shaft, a drive chain engaging said small sprocket and said large sprocket in such a manner that said paddle shafts are driven counterrotationally from said feeder screw, and adjustable idler sprocket means for said chain.

5. The combination according to claim 1, wherein means are provided for retracting and advancing said feeder screw and housing relative to said combustion chamber, which comprises a support structure for said housing and paddle device and drive means therefore, horizontal track means supporting said support structure for movement towards and away from said combustion chamber, and wherein said supply means comprise a downwardly directed neck normally communicating with said upwardly directed neck, and said upward and said downward neck having mating flanges extending in a plane downwardly inclined towards said combustion unit, and so constructed and arranged that retracting said support structure will separate said flanges and expose the paddle device, while forward movement of the structure is adapted to provide wedge action closing the flanges tightly upon one another.

6. The combination according to claim 1, wherein means are provided for maintaining in said combustion chamber a bed of hot fluidized sand, and wherein said delivery end portion of the screw housing is connected to the side of said combustion chamber for delivery of the waste material directly into said bed of fluidized sand.

7. Apparatus for feeding and disposing of dewatered sewage sludge or the like substances, which comprises in combination a combustion chamber, a horizontal feeder screw, a housing wherein said screw is mounted for rotation, said housing having a delivery end portion connected to said combustion chamber in sealed relationship therewith and an upwardly directed vertical supply neck through which the waste material passes downwardly from a source of supply to said screw, a paddle device which comprises a pair of semi-cylindrical internal concavities formed symmetrically in opposite walls of said neck, a horizontal paddle shaft with radially extending paddles mounted for rotation in each of said concavities concentric therewith, said concavities being so constructed and arranged that only when the paddles move substantially downwardly counter-rotationally will they engage the descending feed material between them from both sides so as to pack the material into the screw, whereas during the balance of their rotation moving substantially upwardly within the respective concavities they are shielded from the descending feed material, means for counterrotationally rotating said paddle shafts while rotating said feeder screw, and means for supplying said waste material to said upwardly directed neck and to said paddle device.

8. Apparatus according to claim 7, wherein said paddle shafts are parallel to the axis of the feeder screw.

9. In a sewage treatment disposal system effective to produce dewatered organic waste material for disposal by combustion, the combination which comprises a combustion unit having a combustion chamber, apparatus remote from said combustion unit for feeding said dewatered sludge into said combustion chamber in sealed relationship therewith, which comprises a feeder screw, a housing wherein said screw is mounted for rotation, having an upwardly directed neck through which feed sludge material passes downwardly to said screw, and having a discharge end; a positive progressive displacement pump having a longitudinal rotary progressive pump member coaxially coupled to the discharge end of the feeder screw and a tubular pump housing surrounding the pump member in cooperative pumping relationship therewith, and connected to the discharge end of the housing of the feeder screw; a paddle device which comprises a pair of semi-cylindrical internal concavities formed symmetricaly in opposite wall-s of said upwardly directed neck, a paddle shaft having radially extending paddles mounted forrotation in each' of said concavities concentric therewith, said concavities being so constructed and arranged that only when the paddles move substantially downwardly counter-rotationally will they engage the descending feed material between them from both sides,

whereas during the balance of their rotation moving substantially upwardly within the respective concavities they are shielded from the descending feed material, means for counter-rotationally rotating said paddle shafts while rotating said feeder screw, and means for supplying said feed material to said upwardly directed neck and to said paddle device.

10. In a sewage treatment disposal system effective to produce dewatered organic waste material for disposal by combustion, the combination which comprises a combustion unit having a combustion chamber, a plurality of feeder screws arranged side by side in a horizontal plane, a housing wherein said screws are mounted for rotation, said housing having an upwardly directed neck through which feed sludge material passes downwardly to said screws, and having a discharge end portion for each screw, a positive progressive displacement pump associated with each feeder screw, said pump having a longitudinal rotary progressive pump member coaxially coupled to the discharge end of the feeder screw, and a tubular pump housing surrounding said pump member in cooperative pumping relationship therewith, and connected to the discharge end portion of the housing of the feeder screw, pipe conduit means connecting the discharge end of each pump to respective points of said combustion chamber for delivery of said waste material thereto, a paddle device which comprises a pair of semicylindr-ical internal concavities formed symmetrically in opposite walls of said upwardly directed neck with their axes extending transversely of said feeder screws, a paddle shaft mounted in each of said concavities concentric therewith, said concavities being so constructed and arranged that only when the paddles move substantially downwardly counter-rotationally will they engage the descending feed material between them from both sides, whereas during the balance of their rotation moving substantially upwardly within the respective concavities they are shielded from the descending feed material, means for counter-rotationally rotating said paddle shafts while rotating said feeding screw, and means for supplying feed material to said upwardly directed neck and to said paddle device.

11. The combination according to claim 10, wherein means are provided for maintaining in said combustion chamber a bed of hot fluidized sand, and wherein said pipe conduit means are connected to the side of said combustion chamber for delivery of said waste material directly into said bed for fluidized sand.

12. The apparatus according to claim 10, wherein separate drive means are provided for said paddle device.

13. The apparatus according to claim 10, wherein two pairs of feeder screws are arranged side by side, and a separate drive unit is provided for each pair with the addition of means operable for selectively confining the supply of feed sludge either to the one pair or the other pair of feeder screws.

14. A continuous feeding apparatus for substantially coherent dewatered organic cake material comprising in combination a delivery conduit, a generally horizontal rotating screw feeding to the delivery conduit, a casing closely surrounding the screw open at its upper side at the upstream portion thereof to receive material to be fed by the screw, a generally vertical chute having 0pposed parallel walls providing a material tight duct to the open portion of said casing, a pair of oppositely rotating paddles mounted in said duct with horizontal axes of rotation parallel to each other and said opposite walls, with the paddles when inwardly directed away from said walls arranged to rotate downwardly to pack 1'1 l v the cake material into the screw, each of said side walls having a concavity shrouding the upwardly moving arc of said paddles, said concavities being, semi-circular in cross-section with the paddle ends fitting closely the concavity, whereby the paddles when moving out of the upper portion of the concavities pull the material away from and downwardly with respect to said walls of the chute.

15. The invention according to claim 14, wherein the inner arcs of said paddles are slightly spaced to permit back flow of surplus cake material.

References Cited UNITED STATES PATENTS 3,319,587 5/1967 Albcrtson et a1.

JAMES W. WESTHAVER, Primary Examiner.

4/1961 Snow et al. 103-5 X 

